1. Field of the Invention
The present application relates in general to a surface current heating apparatus, and more particularly to such a heating apparatus suitable for small-scale heating applications.
2. Discussion of the Related Art
A known surface current heating apparatus includes a heat generating tube made of a ferromagnetic material, and an electrically conductive wire extending through the heat generating tube such that the conductive wire is electrically insulated. In operation, an alternating current is applied from an AC power source to the conductive wire, so that a surface current flows near the inner circumferential surface of the heat: generating tube, causing the heat generating tube to generate heat. The heat generating tube is a tubular member made of a steel or other ferromagnetic material. Generally, the conductive wire is electrically insulated at its surface with an organic or inorganic insulator.
The surface current heating apparatus was originally developed for heating a pipe line, and has been used for various applications, as snow-melting or anti-freezing heating devices, industrial heat sources, and heaters such as panel heaters, as disclosed in Japanese Patent Applications laid-open for opposition purpose as Publication Nos. 43-16931 and 52-14854. The snow-melting or anti-freezing heating devices include those for roadways, floors and walls. The industrial heat sources include those for boilers, hot water supplies and plating baths.
Conventionally, the surface current heating apparatus of the type mentioned above uses a heat generating tube which is as long as possible for a particular application of the apparatus. That is, commercially available steel tubes of various nominal lengths are used where the specific heating apparatus allows the use of a steel tube of a particular nominal length. Where the heating apparatus does not permit the use of any of such steel tubes of nominal lengths, due to a limited length of installation space for the steel tube in the apparatus, a steel tube of an appropriate nominal length is cut to a desired length suitable for use in the apparatus.
However, the present inventors discovered that the use of a long heat generating tube or tubes is not necessarily advantageous, and that the use of a relatively large number of heat generating tubes each having a comparatively small length is more advantageous in most cases of small-scale heating or heat generating applications. The inventors recognized potential advantages of a surface current heating apparatus which uses a heat generating member or members in the form of a plate, block or slab having through-holes through which an electrically conductive wire extends.